
/* Copyright 1998 by the Massachusetts Institute of Technology.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of M.I.T. not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 */
#include "ares_setup.h"

#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_ARPA_NAMESER_H
#include <arpa/nameser.h>
#else
#include "nameser.h"
#endif
#ifdef HAVE_ARPA_NAMESER_COMPAT_H
#include <arpa/nameser_compat.h>
#endif

#include "ares.h"
#include "ares_inet_net_pton.h"
#include "ares_platform.h"
#include "ares_private.h"

#ifdef WATT32
#undef WIN32
#endif

struct addr_query {
    /* Arguments passed to ares_gethostbyaddr() */
    ares_channel channel;
    struct ares_addr addr;
    ares_host_callback callback;
    void* arg;

    const char* remaining_lookups;
    int timeouts;
};

static void next_lookup(struct addr_query* aquery);
static void addr_callback(void* arg, int status, int timeouts,
    unsigned char* abuf, int alen);
static void end_aquery(struct addr_query* aquery, int status,
    struct hostent* host);
static int file_lookup(struct ares_addr* addr, struct hostent** host);
static void ptr_rr_name(char* name, const struct ares_addr* addr);

void ares_gethostbyaddr(ares_channel channel, const void* addr, int addrlen,
    int family, ares_host_callback callback, void* arg)
{
    struct addr_query* aquery;

    if (family != AF_INET && family != AF_INET6) {
        callback(arg, ARES_ENOTIMP, 0, NULL);
        return;
    }

    if ((family == AF_INET && addrlen != sizeof(aquery->addr.addrV4)) || (family == AF_INET6 && addrlen != sizeof(aquery->addr.addrV6))) {
        callback(arg, ARES_ENOTIMP, 0, NULL);
        return;
    }

    aquery = ares_malloc(sizeof(struct addr_query));
    if (!aquery) {
        callback(arg, ARES_ENOMEM, 0, NULL);
        return;
    }
    aquery->channel = channel;
    if (family == AF_INET)
        memcpy(&aquery->addr.addrV4, addr, sizeof(aquery->addr.addrV4));
    else
        memcpy(&aquery->addr.addrV6, addr, sizeof(aquery->addr.addrV6));
    aquery->addr.family = family;
    aquery->callback = callback;
    aquery->arg = arg;
    aquery->remaining_lookups = channel->lookups;
    aquery->timeouts = 0;

    next_lookup(aquery);
}

static void next_lookup(struct addr_query* aquery)
{
    const char* p;
    char name[128];
    int status;
    struct hostent* host;

    for (p = aquery->remaining_lookups; *p; p++) {
        switch (*p) {
        case 'b':
            ptr_rr_name(name, &aquery->addr);
            aquery->remaining_lookups = p + 1;
            ares_query(aquery->channel, name, C_IN, T_PTR, addr_callback,
                aquery);
            return;
        case 'f':
            status = file_lookup(&aquery->addr, &host);

            /* this status check below previously checked for !ARES_ENOTFOUND,
             but we should not assume that this single error code is the one
             that can occur, as that is in fact no longer the case */
            if (status == ARES_SUCCESS) {
                end_aquery(aquery, status, host);
                return;
            }
            break;
        }
    }
    end_aquery(aquery, ARES_ENOTFOUND, NULL);
}

static void addr_callback(void* arg, int status, int timeouts,
    unsigned char* abuf, int alen)
{
    struct addr_query* aquery = (struct addr_query*)arg;
    struct hostent* host;
    size_t addrlen;

    aquery->timeouts += timeouts;
    if (status == ARES_SUCCESS) {
        if (aquery->addr.family == AF_INET) {
            addrlen = sizeof(aquery->addr.addrV4);
            status = ares_parse_ptr_reply(abuf, alen, &aquery->addr.addrV4,
                (int)addrlen, AF_INET, &host);
        } else {
            addrlen = sizeof(aquery->addr.addrV6);
            status = ares_parse_ptr_reply(abuf, alen, &aquery->addr.addrV6,
                (int)addrlen, AF_INET6, &host);
        }
        end_aquery(aquery, status, host);
    } else if (status == ARES_EDESTRUCTION)
        end_aquery(aquery, status, NULL);
    else
        next_lookup(aquery);
}

static void end_aquery(struct addr_query* aquery, int status,
    struct hostent* host)
{
    aquery->callback(aquery->arg, status, aquery->timeouts, host);
    if (host)
        ares_free_hostent(host);
    ares_free(aquery);
}

static int file_lookup(struct ares_addr* addr, struct hostent** host)
{
    FILE* fp;
    int status;
    int error;

#ifdef WIN32
    char PATH_HOSTS[MAX_PATH];
    win_platform platform;

    PATH_HOSTS[0] = '\0';

    platform = ares__getplatform();

    if (platform == WIN_NT) {
        char tmp[MAX_PATH];
        HKEY hkeyHosts;

        if (RegOpenKeyExA(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, KEY_READ,
                &hkeyHosts)
            == ERROR_SUCCESS) {
            DWORD dwLength = MAX_PATH;
            RegQueryValueExA(hkeyHosts, DATABASEPATH, NULL, NULL, (LPBYTE)tmp,
                &dwLength);
            ExpandEnvironmentStringsA(tmp, PATH_HOSTS, MAX_PATH);
            RegCloseKey(hkeyHosts);
        }
    } else if (platform == WIN_9X)
        GetWindowsDirectoryA(PATH_HOSTS, MAX_PATH);
    else
        return ARES_ENOTFOUND;

    strcat(PATH_HOSTS, WIN_PATH_HOSTS);

#elif defined(WATT32)
    extern const char* _w32_GetHostsFile(void);
    const char* PATH_HOSTS = _w32_GetHostsFile();

    if (!PATH_HOSTS)
        return ARES_ENOTFOUND;
#endif

    fp = fopen(PATH_HOSTS, "r");
    if (!fp) {
        error = ERRNO;
        switch (error) {
        case ENOENT:
        case ESRCH:
            return ARES_ENOTFOUND;
        default:
            DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n",
                error, strerror(error)));
            DEBUGF(fprintf(stderr, "Error opening file: %s\n",
                PATH_HOSTS));
            *host = NULL;
            return ARES_EFILE;
        }
    }
    while ((status = ares__get_hostent(fp, addr->family, host)) == ARES_SUCCESS) {
        if (addr->family != (*host)->h_addrtype) {
            ares_free_hostent(*host);
            continue;
        }
        if (addr->family == AF_INET) {
            if (memcmp((*host)->h_addr, &addr->addrV4,
                    sizeof(addr->addrV4))
                == 0)
                break;
        } else if (addr->family == AF_INET6) {
            if (memcmp((*host)->h_addr, &addr->addrV6,
                    sizeof(addr->addrV6))
                == 0)
                break;
        }
        ares_free_hostent(*host);
    }
    fclose(fp);
    if (status == ARES_EOF)
        status = ARES_ENOTFOUND;
    if (status != ARES_SUCCESS)
        *host = NULL;
    return status;
}

static void ptr_rr_name(char* name, const struct ares_addr* addr)
{
    if (addr->family == AF_INET) {
        unsigned long laddr = ntohl(addr->addrV4.s_addr);
        unsigned long a1 = (laddr >> 24UL) & 0xFFUL;
        unsigned long a2 = (laddr >> 16UL) & 0xFFUL;
        unsigned long a3 = (laddr >> 8UL) & 0xFFUL;
        unsigned long a4 = laddr & 0xFFUL;
        sprintf(name, "%lu.%lu.%lu.%lu.in-addr.arpa", a4, a3, a2, a1);
    } else {
        unsigned char* bytes = (unsigned char*)&addr->addrV6;
        /* There are too many arguments to do this in one line using
        * minimally C89-compliant compilers */
        sprintf(name,
            "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.",
            bytes[15] & 0xf, bytes[15] >> 4, bytes[14] & 0xf, bytes[14] >> 4,
            bytes[13] & 0xf, bytes[13] >> 4, bytes[12] & 0xf, bytes[12] >> 4,
            bytes[11] & 0xf, bytes[11] >> 4, bytes[10] & 0xf, bytes[10] >> 4,
            bytes[9] & 0xf, bytes[9] >> 4, bytes[8] & 0xf, bytes[8] >> 4);
        sprintf(name + strlen(name),
            "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa",
            bytes[7] & 0xf, bytes[7] >> 4, bytes[6] & 0xf, bytes[6] >> 4,
            bytes[5] & 0xf, bytes[5] >> 4, bytes[4] & 0xf, bytes[4] >> 4,
            bytes[3] & 0xf, bytes[3] >> 4, bytes[2] & 0xf, bytes[2] >> 4,
            bytes[1] & 0xf, bytes[1] >> 4, bytes[0] & 0xf, bytes[0] >> 4);
    }
}
